Transmission losses (TL) to highly impulsive signals generated by three firearms have been measured for two ear muffs, using both a head and torso simulator and a miniature microphone located at the ear canal entrance (MIRE technique). Peak SPL TL have been found to be well approximated by 40 ms short-L eq TL. This has allowed the use of transmissibilities and correction factors for bone conduction and physiological masking appropriate for continuous noise, for the calculation of REAT-type peak insertion losses (IL). Results indicate that peak IL can be well predicted by estimates based on one-third octave band 40 ms short L eq and manufacturer-declared (nominal) IL measured for continuous noise according to test standards. Such predictions tend to be more accurate at the high end of the range, while they are less reliable when the attenuation is lower. A user-friendly simplified prediction algorithm has also been developed, which only requires nominal IL and one-third octave sound exposure level spectra. Separate predictions are possible for IL in direct and diffuse sound fields, albeit with higher uncertainties, due to the smaller number of experimental data comprising the two separate datasets on which such predictions are based.

Prolonged exposure to high levels of occupational noise can cause damage to hair cells in the cochlea and result in permanent noise-induced cochlear hearing loss. Consequences of cochlear hearing loss on speech perception and psychophysical abilities have been well documented. Primary goal of this research was to explore temporal processing and speech perception Skills in individuals who are exposed to occupational noise of more than 80 dBA and not yet incurred clinically significant threshold shifts. Contribution of temporal processing skills to speech perception in adverse listening situation was also evaluated. A total of 118 participants took part in this research. Participants comprised three groups of train drivers in the age range of 30-40 (n= 13), 41 50 ( = 13), 41-50 (n = 9), and 51-60 (n = 6) years and their non-noise-exposed counterparts (n = 30 in each age group). Participants of all the groups including the train drivers had hearing sensitivity within 25 dB HL in the octave frequencies between 250 and 8 kHz. Temporal processing was evaluated using gap detection, modulation detection, and duration pattern tests. Speech recognition was tested in presence multi-talker babble at -5dB SNR. Differences between experimental and control groups were analyzed using ANOVA and independent sample t-tests. Results showed a trend of reduced temporal processing skills in individuals with noise exposure. These deficits were observed despite normal peripheral hearing sensitivity. Speech recognition scores in the presence of noise were also significantly poor in noise-exposed group. Furthermore, poor temporal processing skills partially accounted for the speech recognition difficulties exhibited by the noise-exposed individuals. These results suggest that noise can cause significant distortions in the processing of suprathreshold temporal cues which may add to difficulties in hearing in adverse listening conditions.

Median barriers as a portion of a divided highway are provided to minimize the cross-median crashes. Moreover, median barriers similar to roadside noise barriers could protect people from transportation noise. Thus, there is a need to investigate various median barrier models to identify changes of insertion loss over a simple rigid barrier. In order to estimate the acoustical influence of median barrier's profile in the shadow zone, different median barrier models are presented and their insertion losses are calculated over a frequency range from 50 to 4000 Hz using a two-dimensional boundary element method. The present investigation has clearly revealed that among the profiled median barriers, T-shape, Y-shape, and L-shape provide better performance than that of the other shapes. It is also found that among inclined barriers, V-shape barrier significantly presents higher values of attenuation. Based on the calculation of different geometrics, it has been shown that a further 2 dB (A) in efficiency could be obtained by a better design of the median barrier which is labeled model "L."

Research on road traffic noise and human health in India: Review of literature from 1991 to current

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Dibyendu BanerjeeDOI:10.4103/1463-1741.97255

This article reviews the literature on research conducted during the last two decades on traffic noise impacts in India. Road traffic noise studies in India are fewer and restricted only to the metropolitan areas. The studies over the years have also focused on the monitoring, recording, analysis, modeling, and to some extent mapping related themes. Negligible studies are observed in areas of physiological and sleep research exposure-effect context. Most impact studies have been associated with annoyance and attitudinal surveys only. Little scientific literature exists related to effects of traffic noise on human physiology in the Indian context. The findings of this review search and analysis observe that very little studies are available relating to traffic noise and health impacts. All of them are subjective response studies and only a small portion of them quantify the exposure-effect chain and model the noise index with annoyance. The review of papers showed that road traffic noise is a cause for annoyance to a variety of degree among the respondents. A generalization of impacts and meta-analysis was not possible due to variability of the study designs and outputs preferred.

Occupational noise exposure and noise-induced hearing loss (NIHL) have been recognized as a problem among workers in Indian industries. The major industries in India are based on manufacturing. There are appreciable numbers of casting and forging units spread across the country. The objective of this study is to determine the prevalence of permanent hearing threshold shift among the workers engaged in Indian iron and steel small and medium enterprises (SMEs) and compared with control group subjects. As a part of hearing protection intervention, audiometric tests were conducted at low (250-1000 Hz), medium (1500-3000 Hz), and high (4000-8000 Hz) frequencies. The occurrence of hearing loss was determined based on hearing threshold levels with a low fence of 25 dB. Comparisons were made for hearing threshold at different frequencies between the exposed and control groups using Student's t test. ANOVA was used for the comparison of hearing threshold dB at different frequencies among occupation and year of experience. A P value <0.05 was considered as statistically significant. All data were presented as mean value (SD). Over 90% of workers engaged in various processes of casting and forging industry showed hearing loss in the noise-sensitive medium and higher frequencies. Occupation was significantly associated with NIHL, and hearing loss was particularly high among the workers of forging section. The analyses revealed a higher prevalence of significant hearing loss among the forging workers compared to the workers associated with other activities. The study shows alarming signals of NIHL, especially in forging workers. The occupational exposure to noise could be minimized by efficient control measures through engineering controls, administrative controls, and the use of personal protective devices. Applications of engineering and/or administrative controls are frequently not feasible in the developing countries for technical and financial reasons. A complete hearing conservation programme, including training, audiometry, job rotation, and the use of hearing protection devices, is the most feasible method for the protection of industrial workers from prevailing noise in workplace environments in the developing countries.

Empirical research indicates that children and teachers are exposed to mean sound levels between 65 and 87 dB (A) and peak sound levels of 100 dB (A) in schools, which may lead to hearing loss and mental health problems. A questionnaire containing 13 targeted questions about noise and sensitivity to noise was distributed to 43 teachers aged between 25 and 64 years at five different primary schools in the Cologne municipal area. The small number of interrogated teachers leads to a wide range of deviation and little significance in the results. Thus, several results are reported following tendencies. Significant results are obtained when comparing younger and older teachers and part- and full-time occupation. Teachers experience highest sound levels in the schoolyard, corridors and classrooms, and 68% of the teachers are annoyed by the noise. Specially, teachers older than 45 years of age suffer from sleep disturbances (44%), and 90% of the full-time employees are tired and exhausted in the evening. Work is judged as physical and mental strain by 51% of the whole sample, and 81% of the older teachers report a significant increase of complaints with increasing years of professional activity. Work-related noise may contribute to physical and mental health problems in teachers. Measures to prevent disease, such as early sensitization of the children to the work-related stressor noise by adequate education with noise lights and dosimeters in the classroom and/or equipping rooms with sound-absorbing materials, have to be discussed.